Some of the victims were hit while trying to cross the tracks illegally while others fell from packed trains on Thursday, police spokesperson SR Gandhi said.
At least 13 others suffered injuries, with police blaming the deaths on people attempting to take short cuts in the monsoon rains battering India's financial capital.
"Too many people prefer to take shortcuts," said Gandhi.
About 7.5 million passengers use the overcrowded trains daily on Mumbai's colonial-era rail network, a lifeline for the city's 20 million residents.
An average of 10 people die on the network every day, either from falling off crowded trains or while crossing the tracks.
Nearly 50,000 people were killed in accidents along tracks and on trains across India from 2015 to 2017, according to Indian Railways data.
In May, three teenagers were killed while taking selfies on a railway track in Haryana state.
While Indian trains carry nearly 24 million passengers every day, critics say the ageing network is inefficient, overburdened and often unsafe.
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